Many home and personal care formulations seek to deliver so-called benefit agents to substrates such as cloth, hair and skin. Encapsulation of the benefit agent in particles has been proposed as a means of enhancing delivery, which is advantageous because of the expense of some benefit agents. Delivery of particles per se can also be useful where the particles, even in the absence of specific benefit agents, confer a benefit.
Improved delivery of fragrance is one such benefit that has been highly explored over recent years. However, perceptions of “freshness” depend not only on the positive hedonics provided by fragrance but also on effective control of malodours. For example, malodour control is important on the skin, for example in the underarm, on feet, and on the scalp, as well as on hair, on laundered textiles and on hard surfaces, such as the toilet bowl or drains.
The use of polymeric particles to absorb odours and malodours in formulations is known. For example, US 2011/0021409 and WO 2009/101000 (Henkel) disclose detergents containing porous polyamide particles and their use in deodorant and antiperspirant compositions. The particles are used to absorb fragrances, and unpleasant odours. US 2009/0048365 (IFF) describes an odour absorbing capsule comprising an active ingredient and an encapsulating polymer.
However, we have found that the subsequent retention of the malodour compounds is an area where improvement is required. Often, known particles readily re-release the malodour compounds, along with fragrance compounds.
EP 1 533 365A (IFF) discloses a process for imparting a fragrance to and/or eliminating a malodour from a surface using particles comprising a polymer (preferably ethylene-vinyl acetate copolymer, ethylcellulose, polystyrene or PMMA) having a free volume (which is effected by holes present in the polymer).
US 2011/059179 (Shefer et al) discloses a controlled delivery system for malodour management, which works by absorbing and neutralizing the malodour and releasing an odorous substance to counteract the malodour. The particles have a hydrophobic core and a film forming hydrophilic surface coating polymer.
EP 1 541 121A (Rohm & Haas) describes a system for releasing active ingredients from a composition comprising oil absorbing polymers and a coating comprising water sensitive, surface active polymers. The oil absorbing polymers have an average particle diameter of 20-1000 nm.
Many of these known particles suffer from agglomeration over time, when incorporated into home care and personal care formulations.
We have now found that particles having hydrophobic shell as well as a hydrophobic core, wherein the Tg of the shell is higher than that of the core, are capable of superior malodour absorption and retention of the malodour, and can be successfully incorporated into compositions without causing agglomeration problems.